Good day,
I would probably not use the solution mentioned here using afilnet.com solution, unless you 100% sure this third party company is reliable. This solution is based on third party company solution which will need to get your permission to control your WhatsApp (phone) probably.
Their solution is simply to send HTTP request from SQL Server, which is not related to this specific solution. You send the request to their server, which then send the WhatsApp message.
So what you need is doing the same idea for step 1: sending HPPT Request using Ole Automation Procedures, sp_OACreate, sp_OAMethod
But we can send it to a service which we control - a different solution (web service), which will do the second step : send the WhatsApp messages.
So which web service can we use?
You can develop one on your server using the WhatsApp API. For more information about it, check this link:
https://developers.facebook.com/docs/whatsapp/getting-started/
note: Obviously if you cannot develop such app then you will probably need a third party solution
Note! As much as I remember, there was a request from Microsoft in the UserVoice to add a connector to WhatsApp. If they will do so, then we will be able to solve this issue in a few minutes using Azure Logic apps.